The present invention relates to a method of manufacturing an organic electroluminescent panel, particularly, a method of forming pixels and a color separation method in an organic electroluminescent panel. In the present specification the term xe2x80x9celectroluminescencexe2x80x9d [electroluminescent] will be abbreviated as xe2x80x9cELxe2x80x9d.
A method of manufacturing an inorganic EL panel is disclosed in Japanese Unexamined Patent Application Publication No. 5-108014. In this inorganic EL panel manufacturing method, as shown in FIG. 22, the process whereby a mask plate 19 having a window pattern 19A corresponding to the light emitting film part for pixels of an identical display color is arranged in extreme proximity to the panel substrate (wherein a transparent electrode 2 and insulating layer 17 are laminated on a transparent electrode 1), and in this state, an inorganic light emitting layer 18 of the identical display color is formed into a film selectively and uniformly from a vapor deposition source 20 in a position corresponding to the window pattern 19A on the insulating layer 17, is performed in sequence, while the position of the mask plate 19 is shifted for each color, then light emitting film parts having differing display colors are formed in sequence by shifting the position for each color. This method is referred to hereinafter as the first conventional method.
Additionally, Japanese Unexamined Patent Application Publication No. 7-121056 discloses a manufacturing method for a color filter used in plasma display or liquid crystal display. According to this method, after a substrate on which a photosensitive layer having an organic photoconductive layer is formed has been charged to the desired polarity, and an electrostatic latent image has been formed by selective exposure, a pattern is formed by fixing a developer in which an inorganic pigment is dispersed, said substrate is baked, the organic photoconductive layer is removed, and the desired pattern can be obtained. Hereinafter, this method is referred to as the second conventional method.
Furthermore, pigment dispersion methods which use photolithography can be considered as manufacturing methods for color filters for liquid crystal displays. In such a method, after the substrate has been coated with a photosensitive polymer in which the colorizing pigment has been dispersed, it is exposed through a photomask and then developed, a color pattern is formed by etching, and this process is repeated for each color of red, green, and blue. This method is referred to hereinafter as method of the comparative example.
For reasons such as the occurrence of bending or warping of the mask plate caused by the weight of the mask plate itself or thermal expansion due to radiant heat during vapor deposition and the difficulty in controlling the precise position of the mask plate, problems such as the overlapping of layers and insufficient separation occur. For this reason, this method is defective in terms of difficulty in increasing the screen size from the standpoint of yield. Additionally, the mask plate is formed by opening patterns in a thin metal plate by etching, but the finer the pattern becomes, the more easily the plate can be cut, and the more difficult the manufacture of the mask plate itself becomes. Furthermore, it is necessary to separate the mask plate and substrate as a countermeasure against shorts in the pixels caused by scratches occurring when the mask plate and substrate come in contact, but the vapor deposition material can turn in on itself during vapor deposition, so that there are limitations to refinement.
The second conventional method, whereby an electrostatic latent image on the photosensitive body is developed with an inorganic pigment dispersed developer, then baked, and the photosensitive body is removed, uses an organic material which lacks heat resistance as the light emitting layer, charge transfer layer, etc., and therefore cannot be used in organic EL panels. In the organic EL panel, moreover, since at present there are no white light emitting materials, the use of a color filter is difficult.
Furthermore, in the case of the method of the comparative example, whereby a pigment dispersion system is used in the coloration of an organic EL panel, since the organic EL material is extremely susceptible to moisture, in patterning, after the substrate which has been coated with the organic polymer has been exposed through a photomask, when processes such as developing and etching are performed, pixel defects such as the occurrence and growth of dark spots and exfoliation at the interface between the organic layer and the electrode can easily occur.
Thus, heretofore, there has been no method for manufacturing organic EL panels in which refinement and/or coloration can be realized practically and effectively.
An object of the present invention is to offer a method of manufacturing an organic thin-film EL panel in which the problems described above are solved.
A second object of the present invention is to offer a method of manufacturing an organic thin-film EL panel in which refinement and coloration can be achieved by means of a simple method without damaging pixels in the organic EL panel.
In order to achieve the aforementioned purpose, the manufacturing method of the present invention is characterized by the fact that, in the manufacture of a pixel light emitting layer and pixel electrode formed in an organic EL panel wherein an organic light emitting material is laminated between a pair of opposing electrodes, at least one of which is transparent or semitransparent:
a transparent substrate is prepared wherein a transparent or semitransparent common electrode is formed on at least one face thereof;
a photosensitive thin film having a charge generating layer and charge transfer layer is formed on the aforementioned common electrode;
the aforementioned photosensitive thin film is uniformly charged, and an electrostatic image is formed by exposure in a specified pattern;
the unexposed portions and the exposed portions of the aforementioned photosensitive thin-film are developed using a powder developer, and a separation wall is formed from the aforementioned charged power developer
a light emitting layer, electron transporting layer, and pixel electrode layer are uniformly deposited in that order;
after deposition, using the charge of the aforementioned electrostatic latent image, the aforementioned power developer used in the aforesaid separation wall is removed by transfer, and the laminate is selectively removed together therewith;
pattern formation of the pixel light emitting layer and separation of the pixel electrode layer are performed simultaneously, and a pixel light emitting layer and pixel electrode are formed in a specified pixel pattern.
Furthermore, according to the second characteristic of the present invention, the method whereby a pixel light emitting layer for each color and pixel electrodes are formed so as to be separated from one another in a color organic EL panel wherein an organic light emitting material is layered between a pair of opposing electrodes, at least one of which is transparent or semitransparent, is characterized by the fact that:
a transparent substrate is prepared wherein a transparent or semitransparent common electrode is formed on at least one face thereof;
a photosensitive thin film having a charge generating layer and charge transfer layer is formed on the aforementioned common electrode;
the aforesaid photosensitive thin film is uniformly charged, an electrostatic latent image is formed by exposure in a pattern in a first color among the three colors of red, green, and blue;
the exposed portion or the unexposed portion of the aforementioned photosensitive film is developed using a powder developer, and a first mask, which is composed of the aforementioned powder developer that has been charged and covers the regions other than the pixel region of the aforementioned first color, is formed;
a light emitting layer of the aforementioned first color, an electron transporting layer, and a pixel electrode layer are deposited uniformly in that order;
after deposition, the aforementioned powder developer used in the aforementioned first mask is removed using the charge of the electrostatic latent image, the laminate is selectively removed together therewith, and a pixel light emitting layer and pixel electrode of a pixel pattern of the aforementioned first color are formed;
the aforesaid photosensitive thin film is uniformly charged, an electrostatic latent image is formed by exposure in a pattern in a second color among the three colors of red, green, and blue;
the exposed portion or the unexposed portion of the aforementioned photosensitive film is developed using a powder developer, and a second mask, which is composed of the aforementioned powder developer that has been charged and covers the regions other than the pixel region of the aforementioned second color, is formed;
a light emitting layer of the aforementioned second color, an electron transporting layer, and a pixel electrode layer are deposited uniformly in that order;
after deposition, the aforementioned powder developer used in the aforementioned second mask is removed using the charge of the electrostatic latent image, the laminate is selectively removed together therewith, and a pixel light emitting layer and pixel electrode of a pixel pattern of the aforementioned second color are formed;
the aforesaid photosensitive thin film is uniformly charged, an electrostatic latent image is formed by exposure in a pattern in a third color among the three colors of red, green, and blue;
the exposed portion or the unexposed portion of the aforementioned photosensitive film is developed using a powder developer, and a third mask, which is composed of the aforementioned powder developer that has been charged and covers the regions other than the pixel region of the aforementioned third color, is formed;
a light emitting layer of the aforementioned third color, an electron transporting layer, and a pixel electrode layer are deposited uniformly in that order;
after deposition, the aforementioned powder developer used in the aforementioned third mask is removed using the charge of the electrostatic latent image, the laminate is selectively removed together therewith, and a pixel light emitting layer and pixel electrode of a pixel pattern of the aforementioned third color are formed;
a pixel light emitting layer and pixel electrode are formed in the three colors of red, green, and blue in the respective desired pixel patterns.
By means of the method of manufacturing an organic EL panel according to the present invention, the organic photosensitive body is formed on a transparent or semitransparent common electrode which is formed as a glass or other transparent substrate, and after this organic photosensitive body has been charged, and an electrostatic image has been formed by selective exposure in a specified pattern, an electrostatic latent image is formed in areas other than those parts, the aforementioned electrostatic latent image is developed using a powder developer having a specified granule diameter and charge amount, and a pixel separation wall is formed.
Furthermore, by means of the method of manufacturing a color organic EL panel according to the present invention, an organic photosensitive body that has been formed on the transparent electrode side for each color is charged and exposed, an electrostatic latent image in the areas other than those of the light emitting dots of the color in question is formed (i.e., an area equivalent to the dot width and space of two colors), and using a developer, a tight-fitting mask is formed in the exposed areas.
Finally, by forming uniformly a light emitting layer for that color, an electron transporting layer, and a pixel electrode layer in that order, by, e.g., vapor deposition, and removing the developer that has formed the tight-fitting mask or separation wall from the panel substrate, a process is performed whereby light emitting pixels and pixel electrodes for that color are formed.
The dot pitch and space width of the organic EL panel obtained is determined by the exposure precision and the granule size of the developer, and it is possible to form a fine pattern having a size of about 10 xcexc.
According to the method described above, moreover, since there is no curling in during vapor deposition due to the floating of the mask when a thin film is formed by vacuum vapor deposition using a mask plate that is separated from the substrate, as in the first conventional method described above, there is no color displacement or positional displacement, and a panel having sharp edges can be produced. Since there is no necessity to position the mask or to reduce the vacuum processing, the panel manufacturing process can be accelerated.